Update epair(4) to the new netisr implementation and polish

things a bit:
- use dpcpu data to track the ifps with packets queued up,
- per-cpu locking and driver flags
- along with .nh_drainedcpu and NETISR_POLICY_CPU.
- Put the mbufs in flight reference count, preventing interfaces
  from going away, under INVARIANTS as this is a general problem
  of the stack and should be solved in if.c/netisr but still good
  to verify the internal queuing logic.
- Permit changing the MTU to virtually everythinkg like we do for loopback.

Hook epair(4) up to the build.

Approved by:	re (kib)

1 files changed, 3 insertions, 3 deletions

diff --git a/share/man/man4/epair.4 b/share/man/man4/epair.4
index b93d36ecfd93..8b4d1401dec4 100644
--- a/share/man/man4/epair.4
+++ b/share/man/man4/epair.4
@@ -28,12 +28,12 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 15, 2008
+.Dd July 26, 2009
 .Dt EPAIR 4
 .Os
 .Sh NAME
 .Nm epair
-.Nd Virtual cross-over Ethernet-like interface pair.
+.Nd A pair of virtual back-to-back connected Ethernet interfaces.
 .Sh SYNOPSIS
 To compile this driver into the kernel,
 place the following line in your
@@ -52,7 +52,7 @@ if_epair_load="YES"
 The
 .Nm
 is a pair of Ethernet-like software interfaces,
-which are directly connected by a virtual cross-over cable.
+which are connected back-to-back with a virtual cross-over cable.
 .Pp
 Each
 .Nm